Portable self powered line mountable electric power line current monitoring transmitting and receiving system

ABSTRACT

A method of determining a fault on a power line conductor includes the steps of determining a magnitude and a direction of a load current waveform in the power line conductor with a loop coil and determining a magnitude and a direction of a fault current waveform in the power line conductor with the loop coil. A polarity of the fault current waveform is compared with a polarity of the load current waveform to determine if a change in polarity between the fault current waveform and the load current waveform occurred to determine the direction of the fault. Data representing a fault to at least one remote location is transmitted when a predetermined trigger value is reached.

CROSS-REFERENCE TO RELATED APPLICATIONS

The application claims priority to U.S. application Ser. No. 14/059,483filed Oct. 22, 2013 which claims priority to Provisional Application No.61/740,517 which was filed on Dec. 21, 2012.

BACKGROUND

The present disclosure relates to a multiple parametersensor/transmitter-receiver unit which may be installed on or removedfrom an energized electric power line, such as an overhead power line.With the advent of Smart-Grid applications for electric power systems,there is an ever increasing need for a device that measures electric,mechanical, and environmental parameters of the power line.

In order to address the increasing need for monitoring power lines,devices have been developed that attach directly to the power line.These devices generally require a power source, such as batteries orsolar panels. When utilizing batteries, regular maintenance must beperformed to replace the batteries, which can become costly. When solarpanels are used, the device may only be powered during sunny weatherconditions and during daylight hours. Therefore, there is a need for adevice that is powered from the current flowing in the electric powerline conductor.

Additionally, utility companies invest significant capital into powersystems and want to protect that investment from damage that could occurduring faults, such as when trees fall onto power lines. Many prior artdevices are capable of measuring current. However, the prior art devicesrequire a coil winding to completely surround the power line to measurethe power line frequency load current or fault current of the powerline. This requires the power line to be disconnected to slip the coilaround the power line, or a complex bending mechanism that bends thecoil completely around the power line during installation or unbends thecoil during removal which can lead to failure of the coil windings.Therefore, there is a need for a device which is low maintenance and canbe constantly powered from the electric power line independent ofweather conditions and still provide accurate current data without phaseshift or saturation which is representative of the status of the powerlines that is not susceptible to failure. Also, there is a need for adevice that determines the direction of the fault current which may beopposite to the direction of the power line frequency load current, aswell as a device that measures the high magnitude and high frequency oflightning stroke currents, and their location.

SUMMARY

A method of determining a fault on a power line conductor includesdetermining the magnitude and direction of a load current waveform inthe power line conductor with a loop coil and determining the magnitudeand the direction of a fault current waveform in the power lineconductor with the loop coil. A polarity of the fault current waveformis compared with a polarity of the load current waveform to determine ifa change in polarity between the fault current waveform and the loadcurrent waveform has occurred to determine the direction of the fault.Data representing a fault is transmitted to at least one remote locationif the predetermined trigger value is met.

These and other features of the disclosed examples can be understoodfrom the following description and the accompanying drawings, which canbe briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a right side view of an example sensor transmitterreceiver unit (“STR unit”).

FIG. 2 illustrates a front view of the STR unit of FIG. 1.

FIG. 3 illustrates a cross-sectional view taken along line A-A of FIG.2.

FIG. 4 illustrates a cross-sectional view taken along line A-A of FIG. 2with an example hotstick.

FIG. 5 illustrates another cross-sectional view taken along line A-A ofFIG. 2 with the example hotstick.

FIG. 5 a illustrates an enlarged view of a keyhole slot.

FIG. 6 illustrates another cross-sectional view taken along line A-A ofFIG. 2 engaging a conductor.

FIG. 7 illustrates an example upper magnetic core subassembly.

FIG. 8 illustrates an expanded view of an example upper magnetic coreand an example lower magnetic core surrounding the conductor and anexample power supply transformer.

FIG. 9 illustrates a schematic view of the line mounted power supply,electronics and transmitter-receiver of the STR unit.

FIG. 10 illustrates an expanded view of the lower magnetic core, examplelead screw assembly, and an example hotstick guide tube.

FIG. 11 illustrates the collapsed view of the lower magnetic core, thelead screw assembly, and the hotstick guide tube.

FIG. 12 illustrates a cross-sectional view taken along line B-B of FIG.2.

FIG. 13 illustrates a cross-sectional view taken along line C-C of FIG.1.

FIG. 14 illustrates an exploded view of example support blocks mountingthe upper magnetic core subassembly and example upper and lower jaws.

FIG. 15 illustrates an exploded view of an upper magnetic core mount andthe upper and lower jaws.

FIG. 16 illustrates a cross-sectional view of an example upper housingincluding an example “C” loop coil for measuring the power linefrequency current taken along line E-E of FIG. 2.

FIG. 17 illustrates a cross-sectional view of the example upper housingshowing the “C” loop coil of FIG. 16 and another example “C” loop coilfor measuring lightning stroke current taken along line F-F of FIG. 1.

FIG. 18 illustrates a right side view of the example “C” loop coil.

FIG. 19 illustrates a cross-sectional view of a top end of the “C” loopcoil of FIG. 18.

FIG. 20 illustrates a cross-sectional view of a bottom end of the “C”loop coil of FIG. 18.

FIG. 21 illustrates a cross-sectional view of the “C” loop coil of FIG.18 taken along line D-D of FIG. 18.

FIG. 22 illustrates a right side view of the other example “C” loopcoil, used for measuring lightning stroke current.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate an example sensor transmitter receiver unit(“STR unit”) 1 installed on a power line conductor C for measuring andmonitoring various parameters of the power line conductor C and itsenvironment. The STR unit 1 is formed from a one piece upper housing 2and a one piece lower housing 3. The lower housing 3 is accepted into abead 4 formed on a distal end of the upper housing 2. In this example,the bead 4 which is an integral part of the upper housing 2 is formed bymachining a portion of the upper housing 2 to form a groove on theinside of the bead 4. The lower housing 3 is secured to the bead 4 andthe upper housing 2 by a collar 5. The collar 5 attaches to a hotstickguide tube 13 (FIG. 3) that is secured to the upper housing 2 andextends through the lower housing 3.

In one example, the upper housing 2 and the lower housing 3 are made ofaluminum or other suitable electrically conductive material. Thematerial chosen should accommodate subassembly installation without theuse of external surface fasteners which could generate corona dischargesdue to high voltage being applied to the upper housing 2 and the lowerhousing 3. The upper housing 2 has the advantage of reducing the numberof mating surfaces and eliminating mismatches between multiple castparts which can generate corona discharges and audible noise due toslightly offset sharp edges of the mating surfaces of the adjacentcastings.

Referring to FIGS. 3 and 4, before the STR unit 1 is clamped onto theconductor C, a lower jaw 7 is moved to its fully lowered position spacedfrom upper jaws 6. This allows the conductor C to pass from position “A”of FIG. 3 through a throat T on the left side of the upper housing 2 andonto the upper jaws 6 in position “B” as shown in FIG. 5.

With the lower jaw 7 of the STR unit 1 in its fully lowered position, aspecially designed hotstick 10 is inserted into the bottom of the STRunit 1 and inside the hotstick guide tube 13. In this example, thehotstick 10 is made of an electrically insulated material such asfiberglass. The hotstick 10 includes a hotstick driver assembly 9 (FIG.4) attached to the hotstick 10 with a pin 36. The hotstick 10 providesthe required electrical insulation between the hands of the linemen andthe energized conductor C. A flexible stirrup assembly 11 (FIG. 4)contains a flexible braided conductor 12 which bends out of the way toallow the hotstick driver assembly 9 to enter a hole in the collar 5. Asmentioned earlier, the collar 5 secures the lower housing 3 to the bead4 on the upper housing 2. The collar 5 is fastened to the hotstick guidetube 13 using the set screw 5 a which is screwed into the collar 5 andinto a hole in the hotstick guide tube 13.

With the hotstick 10 and the hotstick driver assembly 9 fully engagedinside the hotstick guide tube 13, the STR unit 1 can be lifted by thelineman with the hotstick 10 onto the conductor C while maintaining theSTR unit 1 securely attached to the hotstick 10.

The upper housing 2 includes two jaw inserts 8, shown in FIGS. 5 and 14,located adjacent the throat T and the upper jaws 6. The two jaw inserts8 include inclined surfaces 8 a and the upper jaws 6 include inclinedsurfaces 6 a. The angle of incline of the inclined surfaces 8 a matchesthe angle of the incline of an inclined surface 2 a on the upper housing2.

The angle of the inclined surfaces 6 a is steeper than the angle of theinclined surfaces 8 a and the inclined surface 2 a to aid in installingthe STR Unit 1 on the conductor C. As the conductor C slides across theinclined surfaces 2 a and 8 a and reaches the steeper incline of theinclined surface 6 a, the STR unit 1 will bounce slightly upward andland in a circular notch 6 b of the upper jaws 6 (See FIG. 4). Thisallows a conductor temperature sensor to be mounted vertically and inthe middle inside the upper jaws 6 and initially extends slightly belowthe circular notch 6 b for the upper portion of the conductor C. The twodifferent inclined surfaces 6 a and 8 a of the jaw inserts 8 and upperjaws 6 prevent the conductor temperature sensor S, shown in FIGS. 3 and4, from becoming damaged since the conductor C firmly lands verticallyin the circular notch 6 b of the upper jaws 6 and pushes the conductortemperature sensor S up to the inside surface of the circular notch 6 b.

In FIG. 3, the lower jaw 7 is located in a pocket P between two legs ofa lower magnetic core 14. The lower jaw 7 is held in place with twospring pins 132 and 133 (FIG. 15) located in the lower jaw 7 that snapinto two holes 15 in a lower jaw holder 16 (FIGS. 10 and 11) which isattached to a bottom block 19 using two screws 20 (FIG. 3). The bottomblock 19 is located adjacent the base of the upper housing 2.

Two identical electrically conductive lower core covers 17 partiallysurround the two legs of the lower magnetic core 14. The lower corecovers 17 are attached to the bottom block 19 on each side of the lowerjaw holder 16 using screws 18 of FIG. 3 on the front right side and oneset of the screws 18 on the back left side (not shown). The front andback lower jaw holders 16 are both held in place by the four screws 20,two in the front and two in the back. The two legs of the lower magneticcore 14 are totally encased by the two lower core covers 17 and thefront and back lower jaw holders 16. Therefore, the lower magnetic core14 is not exposed to any moisture, such as from rain, snow, and ice thatcould enter through the throat T of the upper housing 2 (FIG. 3).

The bottom block 19 contains a conical hole 21 in the center whichprovides a very low friction bearing surface for the semi-circular topof a lead screw 22 (FIG. 3). The lead screw 22 is held in the conicalhole 21 with a retainer plate 23 which has a hole in the middle the sizeof the lead screw 22 diameter and is fastened to the bottom block 19.The lead screw 22 is threaded into the center of a threaded bushing 25.The threaded bushing 25 has a reduced diameter cylindrical lower portionwhich fits inside the hotstick guide tube 13 and a larger diametercylindrical top portion of the threaded bushing 25 is supported on theupper end of the hotstick guide tube 13. Both the threaded bushing 25and the hotstick guide tube 13 are attached to a hotstick guide support26 using two large through bolts 27 and nuts which are placed throughthe holes in a bottom support 28.

Referring to FIG. 2, the upper jaws 6 include two spaced apart jaws andthe lower jaw 7 includes a single jaw aligned between the two spacedapart upper jaws 6. When lower jaw 7 is clamped onto the conductor C,the conductor C is bent slightly upward as the lower jaw 7 extendsupward between the upper jaws 6 creating a bending moment in theconductor C. The bending moment in the conductor C prevents the STR unit1 from sliding down the conductor C, especially when the STR unit 1 ismounted at the point of attachment adjacent a utility pole or towerwhere the slope of the conductor C is at its maximum value. Preventingthe upper jaws 6 and the lower jaw 7 from sliding down the conductor Cat the point of attachment is necessary when the STR unit is being usedto measure sag of the power line conductor.

Referring to FIGS. 5 and 5 a, the bottom support 28 includes an upsidedown “U” shaped cross member and is fastened at each end to the upperhousing with two large threaded screws 29 on each side. The threadedbushing 25 has two small vertical holes 25 a drilled through thethreaded bushing 25 on each side of the threaded hole in the middle forthe lead screw 22. The vertical holes 25 a are countersunk on the topand provide drainage paths for water that can accumulate underneath thebottom block 19 and on top of the bottom support 28 (FIG. 5 a). Thewater then drains through the two vertical holes 25 a in the threadedbushing 25 and drops on the inside of the hotstick guide tube 13 and outthe bottom of the STR unit 1. Therefore, water will not leak into thelower housing 3.

Referring to FIG. 6, the lead screw 22 has a small diameter hotstickguide 30 which is threaded on the inside and is screwed on the bottom ofthe lead screw 22. A pin 31 keeps the hotstick guide 30 from turning onthe lead screw 22. The hotstick guide 30 prevents the inside of ahotstick lead screw driver 33 from coming into contact with the threadson the lead screw 22 and damaging the internal bore of the lead screwdriver 33. It also guides the lead screw driver 33 onto the lead screw22. When the pin 31 engages the lead screw driver 33 the STR unit 1 isready for installation on the conductor C.

The hotstick driver assembly 9 includes the lead screw driver 33, ahotstick driver coupling 32, a rivet 34, a hotstick sleeve 35, the pin36, and the hotstick 10. The hotstick 10 of FIG. 4 rests on the roundedportion of the hotstick driver coupling 32 and the rounded inside bottomof the hotstick guide tube 13. This prevents the lead screw driver 33from applying pressure to the threaded bushing 25 upon installation ofthe STR unit 1 on the conductor C. The lead screw driver 33 and thehotstick driver coupling 32 are each fastened to the hotstick sleeve 35by the rivet 34 and the hotstick sleeve 35 is attached to the hotstick10 with the pin 36. A long narrow vertical slot in the lead screw driver33 allows the pin 31 of the lead screw 22 to be engaged with the leadscrew driver 33 and is free to slide up or down in the vertical slot 37as the lead screw is turned to tighten the lower jaw 7 on the conductorC or to loosen the lower jaw 7 from the conductor C to remove the STRunit 1.

When the hotstick driver assembly 9 is engaged with the lead screw 22 asshown in in FIG. 4, the STR unit 1 is raised to position “A” relative tothe height of the conductor C. The STR unit 1 is then moved toward theconductor C so that the conductor C passes through the throat T of theupper housing 2 and into position “B” as shown in FIG. 5. Once the STRunit 1 is fully supported by the conductor C in position “B”, thehotstick driver assembly 9 is turned clockwise by the installer with thehotstick 10 and allowed to drop down from its position in FIG. 4 to alower position as in FIG. 5. A horizontal keyhole slot 38 of the leadscrew driver 33 is now engaged with the pin 31 of the lead screw 22.With the pin 31 in the horizontal keyhole slot 38, the hotstick driverassembly 9 and the hotstick 10 are secured to the STR unit 1.

In this example, an opening and closing mechanism 39 of FIG. 6 extendsthe lower jaw 7 upward to secure the STR unit 1 on the conductor C.Additionally, the opening and closing mechanism 39 can also retract thelower jaw 7 to remove the STR unit 1 from the conductor C. The openingand closing mechanism 39 includes the lower magnetic core 14, the lowercore covers 17, the lower jaw holders 16, the lower jaw 7, spring pins132 and 133, the bottom block 19, the retainer plate 23, two fasteners24, the lead screw 22, the hotstick guide 30, and the pin 31.

FIG. 6 illustrates the keyhole slot 38 on the lead screw driver 33engaged with the pin 31 on the lead screw 22. As the lead screw 22 isturned clockwise, the opening and closing mechanism 39 moves the lowermagnetic core 14 toward an upper magnetic core 40. The upper magneticcore 40 has two large compression springs 41 to bias the upper magneticcore 40 downward. The compression springs 44 provide pressure to holdboth the upper magnetic core 40 and the lower magnetic core 14 togetherto reduce the magnetic reluctance caused by air gaps 54 (FIG. 8) betweenthe upper magnetic core 40 and the lower magnetic core 14.

The hotstick driver assembly 9 can continue to be turned clockwise evenafter the lower magnetic core 14 begins to mate with the upper magneticcore 40 because the compression springs 41 compress at the top of theupper magnetic core 40. The clockwise motion of the hotstick driverassembly 9 can be achieved either manually or with a battery powereddrill or another rotating device, until the lower jaw 7 is tightenedonto the conductor C. After the STR unit 1 is mounted on the conductorC, the hotstick 10 is turned slightly to the left, or counterclockwise,and the pin 31 will become disengaged from the horizontal portion of thekeyhole slot 38. The hotstick 10 is then free to be removed when the pin31 aligns with the vertical slot 37.

FIGS. 7 and 8 illustrate the bottom of the compression springs 41 areheld in alignment in two cylindrical pockets 42 of two identicalhorizontal upper core blocks 43 which are each used to clamp the uppermagnetic core 40 to two identical magnetic horizontal lower core blocks44. The top of the compression springs 41 are held in place with twoprojections 49 extending downward on the inside of the upper housing 2.The compression springs 41 are totally enclosed by the upper housing 2and are protected from the adverse weather which can cause corrosion.The air gaps 54 between the upper and lower magnetic cores 40 and 14 aretotally enclosed by the upper housing 2 which prevents the air gaps 54from becoming corroded due to moisture from the environment. Thehorizontal upper core blocks 43 and the horizontal lower core blocks 44are clamped around the upper magnetic core 40 on each side using twothrough bolts 45 and two nuts 46 in the front and two through bolts 45and two nuts 46 located in the back of the upper horizontal core blocks43 and horizontal lower core blocks 44.

When the two large compression springs 41 push the upper core blocks 43down, the upper magnetic core 40 is prevented from falling out of a leftcore shoe 50 and a right core shoe 51, by a step 52 located at thebottom of the right core shoe 51 and a step 53 located at the bottom ofthe left core shoe 50.

When the lower magnetic core 14 mates with the upper magnetic core 40,the lead screw 22 can be turned further clockwise to move the two uppercore blocks 43 away from the steps 52 and 53 and further compress thecompression springs 41. The lead screw 22 can continue to be turnedclockwise and compress the compression springs 41 until the lower jaw 7and the upper jaws 6 are tight on the conductor C.

Electrical insulating spools 47 are inserted over each of the throughbolts 45 and electrical insulating washers 48 are inserted under thehead of each through bolt 45 and under each nut 46. The insulatingspools 47 and the insulating washers 48 on each of the through bolts 45prevent shorted electrically conductive paths around the upper magneticcore 40 which is comprised of the four through bolts 45, four nuts 46,the two electrically conductive upper core blocks 43 and the two lowercore blocks 44.

When the upper jaws 6 and the lower jaw 7 are firmly tightened on theconductor C, the compression springs 41 are compressed to their maximumdistance, and thus the maximum compressive force is also applied to thelower magnetic core 14 and the upper magnetic core 40. This decreasesthe size of the air gaps 54 between the lower magnetic core 14 and theupper magnetic core 40 and the magnetic reluctance between the lowermagnetic core 14 and the upper magnetic core 40. Depending on the sizeof the conductor C, varying amounts torque can be applied to thehotstick driver assembly 9 to tighten the opening and closing mechanism39 on the conductor C.

The physical size and shape of the upper jaws 6 and the lower jaw 7 aredesigned such that approximately the same compressive force is appliedto the upper magnetic core 40 and the lower magnetic core 14. In oneexample, there are five different sets of upper and lower jaws 6 and 7that can fit different conductor sizes and types ranging from 0.162inches in diameter and up to 1.17 inches in diameter. The opening andclosing mechanism 39 allows the STR unit 1 to be installed on a widerange of conductor diameters without changing the upper jaws 6 and thelower jaws 7 while maintaining sufficient contact between the uppermagnetic core 40 and the lower magnetic core 14 to complete the magneticcircuit of the power supply transformer 55 of the STR unit 1 whichderives its power from the current flowing through the conductor C topower a power supply module 60 of FIG. 9. Because the STR unit 1 derivespower from the conductor C, batteries or solar cells are not required topower the STR unit 1. The STR unit 1 is powered at all times whencurrent is flowing in the conductor C, even at current levels as low as6.8 amperes and still process data and transmit data at 1 watt powerlevels because of the low threshold of the power supply module 60.

Maintaining a minimum magnetic reluctance insures that a power supplytransformer 55 (FIGS. 8 and 9) will provide the needed secondary voltageV2 and secondary current 12 to operate the power supply transformer 55,sensor electronics module 63, and transmitter/receiver 64. The powersupply transformer 55 includes the upper magnetic core 40, the lowermagnetic core 14, and a coil winding 56. The upper magnetic core and thelower magnetic core form a window W for accepting the conductor C.

The number of secondary turns N2 of wire on the coil winding 56 areoptimized to produce the required secondary voltage V2 and secondarycurrent 12 with a minimum of current I1 in the conductor C. The coilwinding 56 is held in place by two coil bobbins 57 which are supportedlaterally by the two upper core blocks 43 and the two lower core blocks44. Secondary leads 58 a and 59 a of coil windings 58 and 59,respectively, are connected to the power supply module 60 whichmaintains the same level of secondary voltage across leads 61 and 62 forthe sensor electronics module 63 and the transmitter/receiver 64 eventhough the primary current may range from 34 amperes up to 1000 amperes.Lower primary currents of 6.8 amperes are achievable with the lowthreshold current power supply module 60. The power supply module 60contains an energy storage device 256 (FIG. 13) which can power thetransmitter/receiver 64 when the conductor C current ceases to flow. Atransmitting and receiving antenna 81 for the on-boardtransmitter/receiver 64 is mounted on the upper housing 2 (FIG. 12).

Locating the coil winding 56, 58, and 59 on the upper magnetic core 40allows the heat from the coil winding 56, 58, and 59 to escape through avent 65 (FIG. 1) in the upper housing 2. When the conductor sensor Slocated within the STR unit 1 measures the temperature of the conductorC, it is important that the heat from the coil windings 56, 58, and 59does not affect the temperature of the conductor C or the conductortemperature sensor S, which is in electrical communication with thesensor electronics module 63. As shown in FIG. 6, a thermally insulatingbarrier 66 located below the coil windings 56, 58, and 59, allows for amore accurate temperature reading of the conductor temperature byblocking heat from the coil windings 56, 58, and 59.

FIGS. 10-12 and 13 illustrate the lower magnetic core 14 with the lowercore covers 17, the lead screw 22, the hotstick guide tube 13, and otherrelated parts in both exploded and collapsed views. The hotstick guidetube 13 is anchored at the top with the through bolts 27 that extendthrough the bottom support 28 and the hotstick guide support 26. A roundcylindrical milled slot 67 is located along opposing sides of the top ofthe hotstick guide tube 13 to accept the through bolts 27 that supportthe hotstick guide tube 13.

A central hole 70 extends through a base plate support 68 and a baseplate 69 for accepting a bottom portion of the hotstick guide tube 13.The base plate support 68 and the base plate 69 are connected to eachother with four identical threaded screws 71. The hotstick guide tube 13is attached to the base plate support 68 and the base plate 69 with setscrews 72 and 73. Left and right side panels 76 of FIG. 12 are attachedto the base plate support 68 and the bottom support 28 for the lowercore 14 with the use of two identical screws 74 extending through thebottom support 28 and the side panel 76 and at the bottom with twoidentical screws 75 extending through the side panel 76 and the baseplate support 68.

The threaded bushing 25 rests on top of the hotstick guide tube 13 andis prevented from turning relative to the hotstick guide tube 13 using aset screw 77. The left and right side panels 76 not only provide addedstrength, but also provide the physical space to mount the power supplymodule 60, the transmitter/receiver 64, the sensor electronics 63, andsupport left and right lower core guides 78 and 79.

The left lower core guide 78 and a right lower core guide 79 are “U”shaped and guide the opening and closing mechanism 39 such that thelower magnetic core 14 is aligned with the upper magnetic core 40. Eachof the left and right lower core guides 78 and 79 are attached to theleft and right side panels 76 with four threaded screws 80. The lowerhousing 3 is placed over the hotstick guide tube 13 at the bottom andfitted up to the base plate 69 and held in place with the collar 5. Thismeans that once the collar 5 is removed, the lower housing 3 can beremoved thus allowing access to the power supply module 60, sensorelectronics module 63, and the transmitter/receiver 64 of FIG. 9 mountedinside and on the left and right side panels 76 for easy maintenance andrepair.

FIGS. 7 and 12-15 illustrate an upper magnetic core subassembly 40 amounted to the upper housing 2. The left and right core shoes 50 and 51support the upper magnetic core 40 such that the upper magnetic core 40can move freely up and down inside the left and right shoes 50 and 51.The left and right core shoes 50 and 51 are attached to the upperhousing 2 using four support blocks 86 and 87 of FIG. 14, right and leftupper core guides 90 and 93, and four vertical through bolts 94, 95, 96,and 97.

The upper magnetic core subassembly 40 a can be inserted through thethroat T and fastened to the inside of the upper housing 2. A topportion of the upper housing 2 is “C” shaped which provides a surface onthe inside for mounting a “C” loop coil 156 for measuring the power linefrequency current (60 Hz or 50 Hz) and a “C” loop coil 157 for measuringlightning stroke current of 200 kA or higher (FIGS. 13 and 16).

The right core shoe 51 has two identical threaded holes 82 and 83 on thefront and back for a total of four, and left core shoe 50 has twoidentical threaded holes 84 and 85 on the front and back for a total offour as shown in FIGS. 7 and 14. As shown in FIG. 14, two identicalsupport blocks 86 on the right side are placed on the front and back ofthe right core shoe 51 and two identical support blocks 87 are placed onthe front and back of the left core shoe 50.

To align the two right side support blocks 86 with the two sets ofthreaded holes 82 and 83 on the right side of the right core shoe 51,threaded screws 88 and 89 are first inserted into the upper and lowerholes in the right side upper core guide 90 and then through the twoholes in the right support block 86 and screwed into the accommodatingthreaded holes 82 and 83 of the right core shoe 51. The two left sidesupport blocks 87 are held in alignment with the left core shoe 50 byfirst inserting two threaded screws 91 and 92 through the other end ofthe right side upper core guide 90 and then through the holes in theleft side support block 87 and screwed into the threaded holes 84 and 85of the left core shoe 50. The same process is repeated on the back sideby connecting support blocks 86 and 87 to the left upper core guide 93with the backside of the right core shoe 51 and the back side of theleft core shoe 50.

The purpose of the upper core guides 90 and 93 is to insure the two longvertical through bolts 94 and 95 placed through the vertical holes inthe two right side support blocks 86 and two long vertical through bolts96 and 97 placed through the vertical holes in the two left side supportblocks 87 line up with the four threaded holes in four threaded inserts98, 99, 100, and 101, which are embedded in the casting of the upperhousing 2. The two right side support blocks 86 are prevented fromfalling down by inserting the back of a right side upper jaw holder 102and the back of the left side upper jaw holder 103 over the verticalthrough bolts 94 and 95 and threading nuts 104 and 105 onto the twovertical through bolts 94 and 95 and tightening them down, respectively.The two left side support blocks 87 are held in place by inserting thevertical through bolts 96 and 97 through the front hole in the rightside upper jaw holder 102 and the front hole in the left side upper jawholder 103 and threading two nuts 106 and 107 on the vertical throughbolts 96 and 97 and tightening them down, respectively.

Four threaded through standoffs 108, 109, 110, and 111 are screwed ontothe four vertical through bolts 94, 95, 96, and 97, respectively. Thethermal barrier 66 is placed over the four bottom holes of the standoffs108, 109, 110, and 111 and screwed to the standoffs 110 and 111 on thefront left side with two flat head screws 112 as shown in FIG. 15.

FIGS. 2 and 15 illustrate casting fillers 113 and 114 located on theback left and back right sides of the STR unit 1 and secured with roundhead screws 115 which are first inserted through holes in the castingfillers 113 and 114 and then through the two back holes on the right andleft side of the thermal barrier 66 and into the standoffs 108 and 109,respectively.

After the upper magnetic core subassembly 40 a is mounted, the left andright lower core guides 78 and 79 including the opening and closingmechanism subassembly 39 and the left and right side panels 76 areinserted through the bottom of the upper housing 2. (See FIG. 12). Fourscrews 29 are inserted through the two holes on the left and the twoholes on the right of the bottom support 28 and screwed into thethreaded holes of the upper housing 2. It should be noted that duringthe insertion process, the right lower core guide 79, shown in FIG. 12,slides around the outside surface of the right core shoe 51 andunderneath a tab 116 at the top as a weldment on the right upper side ofthe right core shoe 51.

As shown in FIG. 12, the tab 116 insures that the right lower core guide79 fits precisely around the outside of the right core shoe 51 toprovide a near perfect alignment of the lower magnetic core 14 with theupper magnetic core 40. The precise alignment between the upper magneticcore 40 and the lower magnetic core 14 reduces magnetic reluctance bydecreasing the air gaps 54. This results in a decrease in the thresholdcurrent for the operation of the power supply module 60.

Referring to FIGS. 14 and 15, the right side upper jaw holder 102 andthe left side upper jaw holder 103 support the two upper jaws 6 and thejaw inserts 8. The long vertical through bolts 96 and 97 which arescrewed into the threaded inserts 100 and 101 at the top and on theinside of the upper housing 2 fit through top holes 117 and 118 on theback and front of the right side upper jaw holder 102 on the right side.Also, flush mount screws 119 and 120 are inserted on the back andthrough corresponding holes in the right side upper jaw holder 102 andare screwed into the upper housing. The flush mount screws 119 and 120are installed before the upper jaws 6 and inserts 8 are mounted to theright side upper jaw holder 102. The same arrangement for mounting theleft side upper jaw holder 103 is followed using screws 121 and 122.

Right and left upper jaw keepers 123 and 124 prevent the upper jaws 6from dropping down on the inside, because spring pins 126 and 127 arelocated on the outside and when depressed snap into the holes 128 and129 of the right side upper jaw holder 102. The same procedure isfollowed with the left upper jaw keeper 124.

The jaw inserts 8 on the right and left sides of the STR unit 1 and infront of the upper jaws 6 are held in place by inserting threaded bolts130 and 131 into each insert 8 and through the right and left keepers123 and 124 and screwing into the upper jaw holders 102 and 103. Thespring pins 132 and 133 are included in the lower jaw 7 which whendepressed snap into the two holes 15 in the lower jaw holder 16.

The transmitting and receiving antenna 81 for the on-board transmitterand receiver 64 shown in FIG. 9 is mounted on the housing 2. The antenna81 is displayed in FIGS. 1 and 2 and is installed on the top left sidein FIG. 1. The solar sensor assembly 134 is located at the top of thishousing and on its vertical centerline (FIG. 13). The small hole 140located directly to the right of the conductor C allows access andadjustment of the electric power line sag sensor 140 (FIG. 1).

All power quantities are derived from the measurements of the voltage(V) and current (I) waveforms and the angle θ between the measured V andI. The real power P, given in watts is the product of the absolute rmsvalues of the voltage |V| and |I| magnitudes times the cosine of theangle θ. The reactive power Q, given in vars is the product of theabsolute rms values of |V| and |I| magnitudes times the sine of theangle θ, which is either positive for lagging inductive loads ornegative for leading capacitive loads. Therefore, the apparent power isP+jQ. The STR unit 1 measures the current and voltage waveforms forthree phase power flows or single phase power, and the phase anglebetween the current and voltage, or power factor.

Referring to FIGS. 16 and 17, the “C” loop coils 156 and 157 are mountedinside the upper housing 2 such that a vertical center line of the “C”loop coils 156 and 157 are located on a vertical centerline C_(v) of theconductor C located within the STR unit 1. As discussed above, the STRunit 1 is adaptable to a full range of conductors C diameter sizes andinsures each of the vertical centerlines of the “C” loop coils 156 and157 extends through the vertical center line of the conductor C.Additionally, the horizontal centerline C_(H) of the “C” loop coils 156and 157 may vary up or down from the horizontal centerline C_(H) of theconductor C. For this design, there may be a maximum offset of plus orminus 0.75 inches as measured up or down from the horizontal centerlineof the “C” loop coils 156 and 157 and the horizontal centerline C_(H)for the majority of conductors C used in the industry, and there is nomeasureable difference between the measured current flowing in theconductor C and the measured value from the “C” loop coils 156 and 157current signals. Furthermore, the upper magnetic core 40 and the lowermagnetic core 14, which also are located on the vertical centerline ofthe conductor C and mid-way between the two “C” loop coils 156 and 157,can be moved up or down from the horizontal centerline plus or minus0.75 inches with no affect on the measured current from the “C” loopcoils 156 and 157. In addition, the measured output voltage from the “C”loop coils 156 and 157 and thus the current signal is linear for a fullrange of conductor current from 10 amperes to 4017 amperes.

The “C” loop coil 156 of FIG. 18 has an angle θ of 23.4 degrees asmeasured from the vertical center line C_(v) of the “C” loop coils 156and 157 and the conductor C. In another example, the angle θ of the “C”loop coil 156 is between 90 degrees and 0 degrees. Increasing the angleθ increases the number of turns N on the “C” loop coil 156, the voltageoutput, and thus the measured current signal. For current values as lowas 10 amperes through the conductor C, increasing the angle θ may benecessary to obtain an acceptable output voltage from the “C” loop coil156. The angle θ is set at 23.4 degrees in this example to allow the “C”loop coil 156 to fit over the largest size conductor C anticipated andstill fit into the upper housing 2 of the STR unit 1 as shown in FIGS.16 and 17.

The “C” loop coil 156 has the advantage of being slipped over aconductor C while it is energized at high voltage without shutting theconductor C down. In addition, extraneous magnetic flux from current inthe upper magnetic core 40, the lower magnetic core 14, and the powersupply transformer 55 does not affect the output voltage and thus themeasured current signal from the “C” loop coil 156, even when the powersupply transformer 55 windings are shorted. In low to medium voltagedistribution circuits with conductor C currents as low as 10 amperes,the output voltage from the “C” loop coil 156 can be doubled by adding asecond layer coil wound in the reverse direction from the first layercoil. This design can be used for measuring the conductor C linefrequency load current of 60 Hz or 50 Hz, but cannot be used to measurethe higher frequency lightning stroke current of from 1 to 10 MHzbecause the distributed capacitance between the two layers of windingscauses phase shift in the measured current signal. A dielectric coilform 145 located within the “C” loop coil 156 can be rigid. Thisprevents the turns of the first and second coil windings of the doublelayer winding of the “C” loop coil 156 from rubbing together whichavoids failure of the winding insulation had the “C” loop coil been madeflexible.

In this example, the “C” loop coil 156 includes the dielectric form 145which is non-metallic and can be rigid because it is not necessary tobend or flex the “C” loop coil 156 completely around the conductor C toobtain accurate current measurements. In the example shown in FIG. 18,the mean radius of the “C” loop coil 156 is r_(m) for the conductor Cfrequency current measurement which fits into the contoured shape of thehousing 2.

Referring to FIGS. 18-20, a first insulated lead 142 is connected to thestart 143 of a coil wire 144. The coil wire 144 is wound around thedielectric coil form 145. An end 146 of the coil wire 144 is connectedto a central conductor 147 (FIG. 19). The central conductor 147 extendsthrough the center of the dielectric coil form 145 and the coil wire144. An end 148 of the central conductor 147 is connected to a secondinsulated lead 149 (FIG. 20).

The voltage output of the “C” loop coil 156 is measured between thefirst insulated lead 142 and the second insulated lead 149. The firstinsulated lead 142 and the second insulated lead 149 are twisted into apair of wires 150 to eliminate the affects of extraneous magnetic fieldson the voltage output (FIG. 20). In turn, the first and second insulatedleads 142 and 149 are protected by an electrostatic shield 151 toeliminate effects of high voltage electric fields created by theconductor C voltage itself. The shielded first and second insulatedleads 142 and 149 are routed to the sensor electronics module 63, whichconverts the voltage output between the first and second insulated leads142 and 149 into a measured current signal.

The dielectric coil form 145 includes a first pair of conical areas 152at a first end of the “C” loop coil 156 to provide a smooth transitionbetween the central conductor 147 and the second insulated lead 149(FIG. 20). A second pair of conical areas 153 at a second end of the “C”loop coil 156 provide a smooth transition between the end of the centralconductor 147 and the coil winding 144 (FIG. 19). The connection pointsadjacent each end of the central conductor 147 are wrapped with severallayers of tape or other suitable electric insulating material 154 tomake a rigid joint and to reinstitute the dielectric strength ofmaterial removed at the first conical area 152 and the second conicalarea 153 after making the electrical connections to the centralconductor 147.

A protective cover 155 may be added over the coil wire 144 to protectthe coil wire 144 from becoming abraded during mounting of the “C” loopcoil 156 inside the STR unit 1 of the upper housing 2. The protectivecover 155 may consist of a heat shrinkable material that covers the coilwire 144, the first and second conical areas 152 and 153, stubs 158 ateach end of the dielectric coil form 145, and the pair of wires 150. The“C” loop coils 156 and 157 may be mounted to the housing 2 using mountedbrackets 159 attached to the housing 2, of which are in turn attached tothe stubs 158, as shown in FIG. 17.

Also, the “C” loop coil 156 can be used to capture the power linefrequency alternating current (sinusoidal) waveforms of faults in thepower system using the same “C” loop coil 156 used to measure the steadystate load current of the conductor C although the current magnitudesare generally much higher than the steady state load current. Becausethe “C” loop coil 156 includes a winding around a dielectric form,saturation at high currents which would normally happen with traditionaliron core current transformers is prevented.

In addition, the “C” loop coil 156 is capable of capturing motorstarting currents and capacitor switching currents which are commonoccurrences on power systems. This is beneficial because traditionaliron core current transformers produce a phase shift when measuringcurrent. The “C” loop coil 156 does not produce any measurable phaseshift between the current being measured in the conductor C and the “C”loop coil 156 output after integrating the voltage output.

Referring to FIGS. 17 and 21-22, the “C” loop coil 157 is similar to the“C” loop coil 156 except where discussed below and shown in FIGS. 17,and 21-22. The “C” loop coil 157 is used for lightning stroke currentmeasurements. The coil cross section area A_(c) and the number of turnsN may need to be reduced to minimize the high output voltages comparedto the “C” loop coil 156 because of the high rate of change of lightningstroke current. Therefore, the angle θ may be reduced to zero degrees asshown in FIG. 22 to minimize the number of turns N in the “C” loop coil157 for measuring lightning stroke currents. If the output voltages forthe “C” loop coil 157 are still too high for lightning strokes of 200 kAor higher, then the angle θ can be reduced to a negative angle. In orderto assure high accuracy lightning stroke measurements with the “C” loopcoil 157, the “C” loop coil 157 must be placed on the verticalcenterline C_(v) of the conductor C. This is also the case for themeasurements of normal conductor C power line frequency (50 H_(z) and 60H_(z)) steady state load currents, and high magnitude sinusoidal faultcurrents. The “C” loop coil 157 is mounted in a similar fashion, as the“C” loop coil 156 (FIG. 17). With the “C” loop coil 157, the phase shiftbetween the actual lightning stroke current and the measured current inthe conductor C is less than 0.26 degrees even for a lightning strokefrequency of 1 MHz.

Another advantage of the “C” loop coil 156 is the cross sectional areaA_(c) of the “C” loop coil 156 can be made large enough to measure lowconductor currents of 10 amperes or less. Since a large cross sectionalarea A_(c) makes the “C” loop coil 156 become very stiff, this option isnot available in prior art devices that require flexing the loop to openand close the loop completely around the conductor C. Since the “C” loopcoil 156 is not bent completely around the conductor C, the “C” loopcoil 156 can be rigid.

The sensor electronics module 63 receives data from the “C” loop coils156 and 157, processes the data, and sends the data to thetransmitter-receiver unit 64, which sends the data to at least oneremote location via the antenna 81.

The sensor electronics module 63 calculates the total harmonicdistortion of the current and the real time thermal capacity of theconductor C. Since the sensor electronics module 63 collects themeasured current for three phase power systems, the percent ofunbalanced current can be calculated. The percent of unbalanced currentis calculated by dividing the negative sequence current I₂ by thepositive sequence current I₁. The negative and positive sequence currentI₁ and I₂ are derived from the measured “C” loop coil 156 currentwaveforms and the resultant phasor magnitudes and angles between eachphasor.

The sensor electronics module 63 records the fault current waveformsbased on detecting a depression in the post fault voltage and the anglebetween the voltage and fault current. The fault current direction isfound by comparing the polarity of a prefault load current with a postfault current. If there is a change in polarity between the prefaultload current and the post fault load current, then the fault current isin the opposite direction to the prefault load current. If there is nochange in polarity, the fault current is in the same direction as theprefault load current. This feature allows the sensor electronics module63 to determine the direction of the fault current obtained from the “C”loop coil 156 of different STR units 1 mounted on the conductor C to pinpoint the location of the fault along the conductor C. In addition, thefault data collected by the “C” loop coil 156 and the sensor electronicsmodule 63 in each of the STR units 1 can send a transfer trip signal todisconnect electric power equipment and generation interconnected to thepower system which otherwise are unable to detect a fault has occurred,but yet are required by the electric power utility to disconnect fromthe power system during faults.

With multiple spaced apart STR units 1 each including the “C” loop coil156 mounted on the same power line conductor C, the approximate locationof the fault can be determined. If the fault current direction measuredby each of two adjacent “C” loop coils 156 is pointing in the oppositedirections and toward each other, then the fault is located between thetwo adjacent “C” loop coils 156. If the fault current direction measuredby each of the two adjacent “C” loop coils is pointing in the samedirection, but opposite to the direction of the prefault load current,then the fault is upstream from the two adjacent “C” loop coils.However, if the fault current direction measured by each of the twoadjacent “C” loop coils is pointing in the same direction as theprefault load current, then the fault is downstream from the twoadjacent “C” loop coils 156.

To further aid maintenance personnel in determining the actual physicallocation of a fault due to lightning on the conductor C, the multipleSTR units 1 each include the “C” loop coil 157. Each of the “C” loopcoils 157 is mounted on the same power line conductor C to measure thepolarity and direction of the high magnitude lightning stroke current bycomparing the lightning stroke current waveform and its voltagewaveform. The voltage waveform is measured with an example voltagemeasuring device 157 a attached to the conductor C and an electricalground as shown in FIG. 9. Furthermore, lightning stroke current andvoltage data are also transmitted to at least one remote location.

Since the STR unit 1 includes the transmitter-receiver unit 64, the STRunit 1 may transmit and receive data to and from remote locations asshown in FIG. 9. Trigger levels for various parameters measured by theSTR unit 1 and instructions for responding to the trigger levels can besent to the transmitter-receiver unit 64 via the antenna 81 by a remotetransmitter. The trigger levels and instructions are sent to the sensorelectronics module 63 and are stored in a data storage device. Thetrigger levels are either fixed values or rate of change values of aparticular parameter measured by the STR unit 1. Once a parameter meetsthe fixed value or rate of change value, the instructions embedded inthe software on the data storage device in the sensor electronics module63 determines whether or not to transmit the data.

For example, the trigger levels and instructions include a sample rateof change and the integration period of the data that can be increasedor decreased. The sensor electronics module 63 can also utilize triggervalues to determine when steady state collected data is changed totransient state collected data.

In another example, when the measured steady state current data abruptlyincreases in magnitude and the measured steady state voltage dataabruptly decreases in magnitude based on preset trigger values andinstructions from the transmitter-receiver unit 64 of the STR unit 1,the event indicates a fault. Data from the event can be sent to theremote location in the form of a transfer trip signal to disconnectdevices such as distributed generators in the power system. Furthermore,when the fault in the power system has been corrected by electricutility protective devices, then the STR unit 1 can send another signalto the disconnected devices to re-connect them to the power system. Asshown in FIG. 13, the STR unit 1 contains an energy storage device 256(i.e. capacitor) that stores energy which is used to power the STR unit1 when the utility has interrupted the current in the power lineconductor, and allows the unit to transmit fault date to the at leastone remote location.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this disclosure. The scope of legal protection given tothis disclosure can only be determined by studying the following claims.

What is claimed is:
 1. A method of determining a fault on a power line conductor comprising the steps of: determining a magnitude and a direction of a load current waveform in the power line conductor with a loop coil; determining a magnitude and a direction of a fault current waveform in the power line conductor with the loop coil; comparing a polarity of the fault current waveform with a polarity of the load current waveform to determine if a change in polarity between the fault current waveform and the load current waveform occurred to determine the direction of the fault; and transmitting data representing a fault to at least one remote location when a predetermined trigger value is reached.
 2. The method of claim 1, including mounting a plurality of STR units on the power line conductor and determining the location of the fault by comparing the polarity of a fault current and a load current of each of the plurality of STR units.
 3. The method of claim 1, wherein the data includes transfer trip data configured to disconnect a device from a power system in response to a fault.
 4. The method of claim 1, wherein the data includes transfer trip data configured to connect a device to a power system.
 5. The method of claim 1, including receiving the predetermined trigger value from the at least one remote location.
 6. The method of claim 1, wherein the predetermined trigger value includes at least one of a fixed value or at least one of rate of change value of a measured parameter. 